The present invention relates to an assembly for coupling a microstrip circuit to a cavity resonator.
The invention is also directed to a method for coupling a microstrip circuit to a cavity resonator.
A cavity resonator has a structure which can be mathematically modelled as an LC resonant circuit. The dimensions of the cavity determine its resonant frequencies, several of which are possible depending on the principal dimensions of the cavity. The cavity resonator is excited by a transistor and a microstrip circuit connected to the transistor device.
According to conventional technology, microstrip circuits are used in conjunction with dielectric resonators up to 30 GHz frequency. Above this 30 GHz frequency the size of the resonator at high frequencies becomes so small that its Q (quality factor) deteriorates significantly. In addition, the size of the dielectric resonator becomes so small that the reliable placement of the resonator onto the microstrip circuit in mass production becomes extremely difficult.
Waveguide systems operating at millimeter wavelengths typically employ diode oscillators. These combinations are, however, clumsy and expensive.
Combinations of microstrip circuits with cavity resonators have been in use up to frequencies of several GHz, but in the millimeter wavelength range the typical coupling method based on a small probe antenna reaches its limits in terms of manufacturing possibilities.